Method of casting a cylinder head for an internal combustion engine



Feb. 13, 1968 A. STEVENS 3,368,259

METHOD OF CASTING A CYLINDER HEAD FOR AN INTERNAL COMBUSTION ENGINE Filed April 1;, 1963 2 Sheets-Sheet 1 Feb. 13, 1968 A. STEVENS 3,368,259

MFJTHOL) OFUASTING A CYLINDER HEAD F01: AN

INTERNAL COMBUSTION ENGINE l" 1963 2 Sheets-Sheet.

Filed April United States Patent METHOD OF CASTING A CYLINDER HEAD FOR AN INTERNAL COMBUSTION ENGINE Anthony Stevens, Coventry, England, assignor to Humber Limited, Coventry, England, a British company Filed Apr. 3, 1963, Ser. No. 270,392 Claims priority, application Great Britain, Apr. 5, 1962, 13,210/62 2 Claims. (Cl. 29-156.7)

The invention relates to cast cylinders or cylinder heads for internal combustion engines of the kind having at least one valve port at one end of a passageway, the passageway being so curved, adjacent to the port, that the port lies in a plane which is oblique to the main body of the passageway.

The invention provides a cylinder or cylinder head of the above kind which is characterised in that, except for at least part of the inside of the curvature of the passageway, the passageway has a shape and section formed by two cores which can be withdrawn through the two ends of the passageway respectively and in that the said inside of the curvature, or part thereof, is provided by an annular insert around the port serving also as a seat for a poppet valve.

The invention further provides the method of manufacturing a cylinder or cylinder head as just defined which comprises the steps of casting the cylinder or head around two cores to form the passageway and port without forming the inside'of the curvature, withdrawing the cores, without destruction thereof, through the two ends of the passageway respectively, and inserting an annular insert into the port to provide the aforesaid inside the curvature and also a seating for a poppet valve.

In one form of the invention, the cross-section of the portion of the passageway formed by the core which is withdrawn through the port end of the passageway is larger, in one transverse dimension at least, than the crosssection of the other portion of the passageway.

Preferably the cross-section of the annular insert provides on the inside of the ring an inward chamfer on one end face to form the valve seating and a convexly curved surface on the other end to provide the said inside of the curvature of the passageway. The curved surface may start at the inner edge of the chamfer and extend to the opposite end face of the annulus, and it may then merge, without abrupt change, into the passageway.

Externally the annulus may be of cylindrical or slightly tapered form and be a force fit or shrunk fit in a counterbore in the casting.

It is an advantage of the above construction of insert that it allows of variation in the size of the adjacent portion of the passageway. Thus the sides or outer curved part of the passageway may extend to a greater or lesser extent over the convexly curved part of the annulus.

Two specific constructions according to the invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIGURE 1 shows a section through a part of a die-cast cylinder head, and

FIGURES 2 and 3 are part sections in a plane at right angles to that of FIGURE 1 on the centre line of the valve, and show how the cross-section of the passageway may be varied at this position without introducing unduly abrupt changes in the surface.

FIGURE 4 shows a section of a part of a modified diecast cylinder head similar to that shown in FIGURE 1,

FIGURE 5 is a section showing the modified insert in place, and

FIGURES 6 and 7 are part sections on the line 6-6 in FIGURE 5, showing different passageway sizes.

In each of the constructions shown, the passageway is cast using two non-destructible cores which interfit on the line C-D. One core is'withdrawn, after casting, in the direction A and the other, which may be cylindrical with a slight taper, is withdrawn in the direction B. The first core forms the outside of the curvature of the passageway in the region of the valve guide but the two cores leave a sharp corner at C.

An annular insert F is pressed or shrunk into a counterbore in the cast head. This has a curved surface EC which forms the inside of the curvature of the passageway.

It is usually desirable that the diameter of the passageway in the region of the valve is larger than the straight portion in order to allow for the volume occupied by the valve and its guide. Furthermore it is desirable to be able to vary the size of this part of the passageway.

The drawings show (FIGURES 2 and 3 and also FIG- URES 6 and 7) how this may be done, using cores of different sizes for this part, without causing unduly sharp changes in the contour of the walls, due to the curvature of the surface EC.

It is not essential that the Whole head is die-cast. The technique employed may use a combination of die-casting with solid cores for the ports and passageways and sandcasting for the remainder of the head.

I claim:

1. In the manufacture of a cylinder head for an internal combustion engine the method of forming a passageway in the head which comprises the steps of:

(a) casting molten metal around a bent core composed of two straight core parts meeting at an obtuse angle, the two core parts being shaped around the outside only of the bend to merge into one another in a curve,

(b) allowing said molten metal to solidify,

(c) withdrawing the core parts axially away from one another to leave a bent passageway composed of two straight portions which make an obtuse angle and merge in a curve around the outside of the bend,

(d) inserting into one portion of the passageway and up to the bend therein an annular insert which constitutes a lining for the passageway portion adjacent the bend and is of internally curved configuration in the axial direction to provide a curved formation for the inside of the bend.

2. The method as claimed in claim 1 in which the annular insert serves also as a seat for a poppet valve.

References Cited FOREIGN PATENTS 321,321 11/1929 Great Britain. 744,250 11/ 1944 Germany.

JOHN F. CAMPBELL, Primary Examiner.

RICHARD WILKINSON, FRED E. ENGELTHALER,

I Examiners.

A. L. SMITH, PAUL M. COHEN, Assistant Examiners. 

1. IN THE MANUFACTURE OF A CYLINDER HEAD FOR AN INTERNAL COMBUSTION ENGINE THE METHOD OF FORMING A PASSAGEWAY IN THE HEAD WHICH COMPRISES THE STEPS OF: (A) CASTING MOLTEN METAL AROUND A BENT CORE COMPOSED OF TWO STRAIGHT CORE PARTS MEETING AT AN OBTUSE ANGLE, THE TWO CORE PARTS BEING SHAPED AROUND THE OUTSIDE ONLY OF THE BEND TO MERGE INTO ONE ANOTHER IN A CURVE, (B) ALLOWING SAID MOLTEN METAL TO SOLIDIFY, (C) WITHDRAWING THE CORE PARTS AXIALLY AWAY FROM ONE ANOTHER TO LEAVE A BENT PASSAGEWAY COMPOSED OF TWO STRAIGHT PORTIONS WHICH MAKE ON ABTUSE ANGLE AND MERGE IN A CURVE AROUND THE OUTSIDE OF THE BEND, 